1. Field of the Invention
The present invention relates to the field of resistor strings and resistor string matrices.
2. Prior Art
The sources of Integral Non-Linearity (INL) and Differential Non-Linearity (DNL) in an integrated circuit resistor string can be generalized as the random mismatch between two adjacent resistors due to process imperfections, contact resistance, mask tolerances, diffraction effects, etc., and the macro-scale (i.e., greater than the dimensions of an individual resistor) resistivity gradients across the structure. To reduce such errors, techniques are known for laying out the resistor string in a manner to reduce the effect of the process variations. Such a prior art resistor string for reducing INL may be seen in FIG. 1.
Also known is a technique for switching between voltage taps so that charge on the various parasitic capacitances of the array cancel during a tap change, resulting in very low matrix perturbation (see U.S. Pat. No. 6,507,272). This technique is also used with the present invention.